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FOOD-BORNE DISEASES Introduction • Causes of food-borne diseases/illnesses: 1. Chemical toxins (‘residues’) 2. Biotoxins – endotoxins & exotoxins 3. Infectious agents – exogenous & endogenous (‘zoonoses’) 2 Introduction contd endotoxins & exotoxins lipopolysaccharide (LPS) : protein part of bacterium : extracellular no toxoid : toxoid low potency : high potency low specificity : high specificity 3 Mode of action of some bacterial toxins S. aureus – A (alpha-toxin) E. coli – B (shiga toxin) C. botulinum – C (exo-enzyme) September 2005 116.407 VPH & MH 4 Introduction contd • Food hygiene vs food safety food hygiene – microbiological safety of food food safety – abscence of chemicals/residues • Not necessary to have ‘sterile’ food 5 Prevention of food-borne diseases • Organisms characteristics 1. 2. 3. 4. where from types & strains behaviour in food survive or are killed by measures to inactivate 6 Prevention of food-borne diseases, contd • Food – characteristics Water activity (aw), pH and temperature 7 What influences occurrence of food-borne diseases/illnesses? • • • • Food source Food storage Food preparation Food handlers 8 What influences occurrence of food-borne diseases/illnesses? • Time-temperature abuse • Infected food handlers or inadequate hygiene during handling of food • Consumption/use of unsafe food sources 9 Types of illnesses/diseases • Upper GIT – nausea & vomiting • Lower GIT – cramps & diarrhoea • Neurological signs • General symptoms 10 Types of illnesses/diseases Upper GIT signs Nausea, retching, vomiting, abdominal pain, diarrhoea & prostration • S. aureus and its toxins • B. cereus and its toxin 11 Types of illnesses/diseases Lower GIT signs Lower abdominal cramps & diarrhoea • Clostridium perfringens, Bacillus cereus • Salmonella, Shigella, ET E. coli, Yersinia enterocolitica, Campylobacter jejuni, Vibrio cholera 12 Types of illnesses/diseases Lower GIT signs, continued Lower abdominal cramps & diarrhoea • Giardia intestinalis • Cryptosporidium parvum 13 Types of illnesses/diseases Neurological signs Visual disturbances, vertigo, tingling sensation & paralysis • Clostridium botulinum 14 Types of illnesses/diseases General symptoms Fever, chills, malaise, prostration, aches, swollen lymph nodes • S. typhi, L. monocytogenes, C. jejuni • Hepatitis A 15 Risks of contracting foodborne disease depend on: • Host susceptibility Age General health 16 Infective dose • Frequently exptrapolated • Feeding studies (healthy, young adult volunteers) • Estimates (data from outbreaks) • ‘Worst case’ estimates 17 Risk assessment – variable infective doses • Interaction – food substrate & environment • pH susceptibility • Type and strain 18 Control of food contamination • Micro-organisms in food & water shellfish fruits & nuts beans watermelons spices & herbs vegetables 19 Control of food contamination • Infection of animals – milk, eggs or meat • Contaminated skins and guts - slaughter & dressing 20 Pathogenic Bacteria • Salmonella spp. - GIT / Hide • E. coli O157:H7 - GIT • Campylobacter spp. - GIT (esp. poultry) • Staphylococcus aureus toxin - Human (nostrils and hands) • Yersinia enterocolitica - GIT • Listeria monocytogenes - Soil, hide, faecal material • C. botulinum, C. perfringens - Soil, hide, faecal material 21 Control of food contamination • • • Ideal = growing & harvesting stages But – ‘world is not sterile’ Prevent, reduce or limit by: Not allowing products from clinically ill animals to enter food chain Classical meat inspection - gross HACCP - microscopic 22 The chain of production from ‘farm to fork’ of food from animals Production Farm, Feedlot, Fishing site Processing Slaughter Plant, Cannery, Packer, Food Factory Final preparation and cooking Final Kitchen: commercial, institutional or domestic 23 The chain of production from farm to fork prevention can occur at each step Production Processing Feed, water, manure treatment, biosecurity, probiotics, vaccines HACCP, slaughter hygiene, pathogen reduction and elimination (pasteurization, irradiation) Final preparation Cooking, preventing cross-contamination, and cooking worker education and hand washing 24 Prevention of Food Poisoning WHO ‘ten golden rules’ • • • • • Food processed for safety Thoroughly cook Eat immediately Store carefully Reheat thoroughly 25 Prevention of Food Poisoning WHO ‘ten golden rules’ contd • • • • • No contact between raw & cooked Wash hands Keep food preparation surfaces clean Protect from pests Use potable water 26 Food-borne disease outbreaks & food spoilage • Contamination with undesirable micro-organisms • Unacceptable levels of microorganisms • Treatment did not result in inactivation 27 Food-borne disease outbreaks & food spoilage • • • • Preventing/limiting contamination Preventing/limiting spread Preventing growth Preventing survival of organisms & persistence of metabolites 28 Microbiological/chemical hazards • Micro-organisms – part of nature Chemicals – many are man-made • Micro-organisms change numbers • Uneven distribution in food • Clinical symptoms – acute • Variable consumer susceptibility 29